\documentstyle{letter}
\begin{document}
\address{476 Memorial Drive \\ Cambridge, MA  02139}
\signature{George Madrid \\ MIT Class of '91}
\begin{letter}{Mr.\ and Mrs.\ Louis Madrid \\ 457 Tampico Way \\
Pensacola, FL  32506}
\opening{Dear Mom and Dad,}

Body

\closing{Sincerely,}
\ps{}
\encl{}
\cc{}
\end{letter}
\end{document}